Method and apparatus for drying coal



Oct. 16, 1962 R. DOWNING METHOD AND APPARATUS FOR DRYING COAL Filed March 22, 1960 4 Sheets-Sheet 1 A A x z T A a R NW L R 2 mw w A i s 3 '7 6 QB om Q. Mm A A a m A F I I g l A A S R H I f 1| I INVENTOR Ricunnu DOwmNG Tmwf gm HTTORNEXS Oct. 16, 1962 R. DOWNING 3,058,229

METHOD AND APPARATUS FOR DRYING COAL Filed March 22, 1960 4 Sheets-Sheet 2 INVENIOR Racumw Dowmue Tam: a To}? HTT RN 5 1962 R. DOWNING 3,058,229

METHOD AND APPARATUS FOR DRYING COAL Filed March 22, 1960 4 Sheets-Sheet 5 INVENTQR Rucmuw IDowuma E s- E W355;

Oct. 16, 1962 R. DOWNING METHOD AND APPARATUS FOR DRYING COAL 4 Sheets-Sheet 4 Filed March 22, 1960 INVENTOR Rmumtu DowmNG HTTORNEYS United States Patent $358,229 METHOD AND APPARATUS FOR DRYING CGAL Richard Downing, Lyman Circle, Shaker Heights, Ohio Filed Mar. 22, 1960, Ser. No. 16,806 10 Claims. (Cl. 3423) The present invention relates to a method and apparatus for drying coal and more particularly to a method and apparatus for drying coal at the mine, or at a stock pile.

Mine run coal varies in size and contains a considerable amount of surface moisture. Usually it is desirable to remove a substantial portion of the surface moisture by drying the coal before shipping it to market. If the coal is to be subjected to an air cleaning operation for removal of impurities, the need for drying the coal is particularly imperative since conventional air cleaners are not adapted to handle coal with a high surface moisture content.

Before the present invention, known driers were capable of drying either the fines, or the larger particles of coal, but not both. Thus it was necessary either to utilize two kinds of driers, or to leave the larger particles undried. In addition, it was necesary to subject the coal to sizing screens while the coal was still moisture laden, thus resulting in screen clogging and consequent improper separation of the fines.

Moreover, the drying operation itself was costly and slow. The old machines were able to turn out only approximately 70 tons per hour, and since most of the machines utilized coal stoked furnaces as the source of heat for the drying medium the cost in installation, labor and fuel was great.

Further, the handling of the coal dust resulting from the drying operation has always been a problem, due to the noxious nature of the fumes and of the highly inflammable and explosive character of the dust.

A further problem with previously known driers has been that frequently a great deal of time and effort had to be expended to put them in operation after idle periods, and that once they were in operation it has been diflicult to control the actual moisture content of the coal upon completion of the drying operation. I

An object of the present invention is to provide a method and apparatus for drying coal which vw'll effectively dry coal in sizes up to 4" x O and which will thus permit the drying of substantially all the coal prior to the screening operation. Thus, two kinds of driers will not be needed and screen clogging will be virtually eliminated.

A further object of the present invention is to provide a method and apparatus for drying coal wherein some of the dust which separates from the coal during the drying operation is used as a fuel for the drying medium, thus substantially cutting drying costs and increasing the quantity of coal which can be dried in a given period. A rotary kiln embodying the present invention 43 feet long and 6 feet in diameter has dried 125 tons per hour and is capable of turning out up to 150 tons per hour of 1 /2 X 0 coal.

A further object is to provide a safe and self-contained method and apparatus for drying coal, wherein the coal drying, dust capturing, dust disposal, and fuel production are all combined in the sarne apparatus.

A further object is to provide a method of drying coal wherein the moisture content of the dried coal is automatically controlled, and wherein the operation may be commenced within minutes even though the apparatus has been idle for an extended period of time.

The foregoing objects are accomplished by cascading the coal in a kiln while moving it from one end of the kiln to the other in the presence of a current of heated drying medium, capturing the coal dust which separates 3,058,229 Patented Oct. 16, 1962 from the coal, and using some of said coal dust as a fuel for heating the drying medium.

Other features and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings.

Referring to the drawings,

FIG. 1 is a side elevation partly broken away of a preferred apparatus for carrying out the invention;

FIG. 2 is a top plan view of the apparatus;

FIG. 3 is a partial cross-sectional end view of the storage bin and combustion chamber taken along lines 33 in FIG. 1;

FIG. 4 is a cross-sectional top plan view of the combustion chamber taken along lines 4-4 in FIG. 1;

FIG. 5 is a cross-sectional side elevation of the gas and an air inlet feed for the combustion chamber;

FIG. 6 is a cross-sectional end elevation of the rotary kiln taken along lines 6-6 in FIG. 1; p

FIG. 7 is a cross-sectional view of the roller flanges taken along lines 7-7 in FIG. 6;

FIG. 8 is a schematic diagram of the electric circuit for the temperature actuated feed control.

Referring again to the drawings, moisture laden coal is suitably fed into a kiln from a hopper 22 which is fed by a conveyor'23. The kiln may take the form of an inclined rotary drum 30 as shown in FIG. 1. A pair of rollers 41 which are journaled in bearing block 43 mounted on a frame 40 may rotatably support one end of the kiln by engaging external ring 44, and another pair of rollers 4'5 and 46 journaled in bearing block 47 may support the other end of the kiln by engaging an external ring 43. A pinion 4:9 driven by a motor '50 may rotate the kiln by engaging an external gear 5 1 on the drum. A pair of rollers 52. and 53 journaled in frames 54 and 55 may ride against the external ring 48 so as to prevent the kiln from sliding axially. I

The inner periphery of the kiln may contain a series of radially projecting blades 33 which are arranged in annular rows, said blades being substantially parallel to the axis of the kiln. The blades'may be providedwith flanges 34, as shown in FIG. 6, which are slightly out of line- *with those in an adjacent row as shown in FIGfl.

As a result of the aforesaid arrangement of blades, the coal is continually cascaded during its journey from the inlet opening 31 to the discharge opening 32 of the rotating kiln, thereby resulting in the exposure of a large percentage of the surface area of the'coal to the drying medium.

The angle of incline of the drum may be'adjusted prior to operation by raising and lowering the drum by way of suitable hydraulic jacks (not shown). It has been found that an incline of in one foot is a preferred adjustment.

During its journey, the cascaded coal is subjected to the drying action of a current 'of warm drying medium which may enter the kiln from a combustion chamber 110. The combustion chamber is in open communication with the kiln, through an inlet opening 31 and a tempering chamber 115. The current of heated drying medium not only dries the coal but also serves as a carrier for the coal dust which emanates from the coal'during its" traverse of the kiln.

Y The mixture of drying medium and coal dust flows from stock pile as by a screw conveyor '64 driven by a motor 65. 4

From the stack 60 the mixture of coal dust and drying medium may be conveyed directly to the combustion chamber, and utilized for drying the coal within the kiln.

However, a preferred means of carrying out the invention is to separate the coal dust from its drying medium carrier, as by a cyclone separator 70, storing some of the dust, as in a storage bin 85, and regulating the feed of the dust from the storage bin to the combustion cham her in accordance with the temperature of the drying medium in the stack 60. One way of regulating the feed is to utilize a thermostat 66 which is connected in circuit with a motor 91 that is used for rotating angers 89 and 90 as shown in FIG. 3.

Referring again to FIG. 1, as a preferred embodiment of the invention, the drying medium and dust mixture flowing through the stack may enter the separator through a conduit 67. The drying medium is drawn through the separator by a fan 71 from whence it is discharged to the atmosphere, while the dust is collected at the bottom of the separator.

The dust may be drawn from the separator in any suitable way, as by a rotating butterfly valve 75, which is driven by a motor 76 and may then be conducted into the combustion chamber.

If desired, some of the dust may be discharged from the system by a screw conveyor 77 driven by a motor 76 and returned to the dried coal, or may be used as fuel for some other operation. That which is intended for use in the combustion chamber is conducted to it either through a conduit which connects directly to the chamber, or through a conduit which connects to a storage bin 85 from which it is fed into the chamber. Where a storage bin is used, the dust to be burned is withdrawn from the conveyor through an opening 79 in a wall of the conveyor casing 78 and the rate of removal may be controlled by a slide valve 80. The dust may then be conveyed through a conduit 81 to the storage bin 85. A preferred method of conveying the dust to the storage bin is to utilize a fan 82 which is driven by a motor 83 and which blows the dust through the conduit 84 to the storage bin.

In the structure of FIG. 3, the dust flowing through conduit 84 may enter the storage bin through an opening 86 in the upper portion of the bin. The dust drops to the bottom of the bin and the air is removed from the bin through conduit 87 and conveyed to the stack. It is to be understood that the bin is closed except for the inlet opening 86 and discharge opening 88, wherefore any excess dust in the bin will be conveyed with the air to the stack for recirculation through the separator. As shown, the discharge opening 88 in the bin is larger than the inlet opening 86 as a result of which suflicient dust will remain in the bin to provide an adequate supply for maintaining the desired temperature in the kiln.

To regulate the flow of fuel from the bin to the combustion chamber so as to maintain a substantially constant stack temperature there is shown in FIG. 1 a thermostat 66 in the stack which is connected in circuit with the motor 91, shown in FIG. 3. The thermostat is set to maintain a substantially constant predetermined temperature in the stack such, for example, as 125 F. In the mechanism illustrated, the thermostat controls the operation of a motor 91, shown in FIG. 3, which in turn controls the movement of feeding angers 89 and 90 which are located beneath the storage bin 85 and are arranged to draw dust therefrom and to discharge it into the combustion chamber. Preferably there are two angers, one a right and the other a left hand spiral, which are mounted upon a common shaft 16 and are rotated by the motor 91. Inlet openings 92 and '93 provide communication between the bottom of the bin and the respective angers while discharge openings 94 and 95 provide communication between the augers and conduits 96 and 97 which lead directly into the combustion chamber.

1 To propel the dust into the combustion chamber and to provide sufficient oxygen to support combustion we provide a compressor 98 shown in FIG. 1 which forces air into a manifold 99 from whence branch conduits 100 and 101 shown in FIGS. 3 and 4 extend into the combustion chamber on opposite sides of a gas pilot flame which is fed by gas pipe 117, said pilot flame is likewise supplied with air through a branch conduit 118 from the manifold 99 in order to support combustion. As shown in FIG. 4 two nozzles 103 and 104 convey dust into the combustion chamber and are disposed at an angle of about 15 degrees with respect to the axis of the gas nozzle 105. In this way the two jets of coal dust are brought together within the combustion chamber in the region of the outer end of the flame from the gas flame. The gas flame thus serves to ignite the coal dust and, so long as it is in operation, to maintain it in ignited condition so long as it is moving into the combustion chamber. A motor 107 shown in FIG. 1 drives compressor 98.

Secondary air for supporting combustion may be introduced into a burner 109 through openings 112 in a wall 111 thereof as shown in FIG. 5. As shown in FIG. 1 tertiary air may be supplied from the atmosphere by way of openings 108 in the wall of the combustion chamber 110. From the combustion chamber 110, the heated gases flow into a mixing or tempering chamber 115 positioned between the combustion chamber and the kiln. Additional openings 116 within the Wall of the chamber 115 admit additional air for supporting combustion and for tempering the gases as desired, so as to assist in maintaining the desired degree of temperature within the kiln. In practice a temperature of 2400 degrees at the entrance to the kiln has been found to be satisfactory where the surface moisture of the coal to be dried is approximately 10 percent. By maintaining the temperature of the exhaust gases in the stack at degrees, the moisture in the coal at the discharge end of the kiln can be reduced to approximately 1% to 2 percent.

The movement of a current of heated drying medium flowing through the kiln and around the tumbling particles of coal operates effectively to dry coal in a range of sizes greater than that which could be dried in any known apparatus. Additionally, the method provides for economy of operation and assures a continuous process of drying.

A further advantage of the present invention is the fact that the apparatus may be shut down for extended periods of time and then restarted immediately without a great loss of time in building up the temperature to the desired degree. The invention therefore is well suited for use in locations where it is desired to operate it during the daytime and to shut it down at night.

A further advantage of the apparatus is that it lends itself to adaptability to the location where it is used and that it may readily be dismantled and transported from place to place and reassembled quickly for subsequent use at a different location.

I claim:

1. An apparatus for drying coal, comprising in combination, a rotary kiln having an inlet opening adjacent one end adapted for receiving a heated drying medium and for receiving lumps of coal which are to be dried by the heated drying medium, outlet means adjacent the other end of the kiln, motor means for rotating the kiln, blade means mounted inside the kiln for tumbling the coal lumps, said blade means operating to move the coal lumps toward the outlet end of the kiln, and to cascade them in the. path of the drying medium, whereby the drying medium becomes laden with coal dust, chute means adjacent to and in communication with the lower portion of the outlet means of the kiln for discharging the dried lumps of coal from the system, stack means in communication with the upper portion of the outlet means of the kiln so as to provide an escape for the coal dust laden drying medium, separating means in communication with the stack for separating the coal dust produced by the drying operation from its drying medium cam'er, coal dust storage means having an inlet port in communication with the separating means and having at least one outlet port, a combustion member having an inlet in communication with said outlet port for receiving at least some of the coal dust therefrom, an inlet for receiving air and an outlet in communication with the inlet opening of the kiln, ignition means for burning the coal dust in the presence of in the combustion member, and feeding means for feeding the coal dust from the outlet port of the storage means to the combustion member.

2. An apparatus according to claim 1 including heat responsive means located at a predetermined point in the apparatus adjacent the heated drying medium and driving means operably connected to said feeding means and controlled by the heat responsive means and operating to regulate the coal dust feed in accordance with the temperature sensed by the heat responsive means.

3. An apparatus according to claim 1, wherein the storage means has at least one other outlet port in communication with the apparatus intermediate the combustion chamber and the inlet port of the storage means and operating to provide recirculation of a portion of the dust which accumulates in the storage means.

4. An apparatus according to claim 1 including blade means mounted on the kiln for tumbling the coal.

5. A method of drying coal at a mine comprising taking a gaseous drying medium and heating it by a combustion process, taking moisture laden lumps of coal and tumbling them in a container while causing the coal lumps to move through the container in a generally uniform direction, passing the heated gaseous drying medium in a current across the coal lumps as they move through the container, the tumbling of the coal lumps combined with the passing of the heated gaseous drying medium across the coal lumps serving to dry the coal lumps and to cause coal dust to emit from the coal lumps, thereby causing the gaseous drying medium to become coal-dust laden, removing the coal-dust-laden gaseous drying medium from the container, transporting the coal dust-laden gaseous drying medium thus obtained to the said combustion process and burning it as a fuel in the said combustion process, and removing dried lumps of coal from the container as an end product, said dried lumps being uncrushed and of sufficitently large sizes, relative to their sizes prior to the drying operation, that the said dried coal lumps are suitable for shipment from the mine as lump coal.

6. A method of drying coal at a mine comprising taking a gaseous drying medium and heating it by a combustion process, taking moisture laden lumps of coal and tumbling them in a container While causing the coal lumps to move through the container in a generally uniform direction, passing the heated gaseous drying medium in a current across the coal lumps as they move through the container, the tumbling of the coal lumps combined with the passing of the heated gaseous drying medium across the coal lumps serving to dry the coal lumps and to cause coal dust to emit from the coal lumps thereby causing the gaseous drying medium to become coal dust-laden, removing the coal dust-laden gaseous drying medium from the container, separating at least some ofi the coal dust from the drying medium, transporting at least a portion of the coal dust thus separated to the combustion process and burning it as a fuel in the said combustion process, and removing the dried coal from the container as an end product, said dried coal lumps being uncrushed and of sufiicierrtly large sizes, relative to their size prior to the drying operation, that the said dried coal lumps are suitable for shipment from the mine as lump coal.

7. A method of drying coal at a mine comprising taking a gaseous drying medium and heating it by a combustion process, taking moisture laden lumps of coal and tumbling them in a container While causing the coal lumps to move through the container in a generally uniform direction, passing the heated gaseous drying medium in a current across the coal lumps as they move through the container, the tumbling of the coal lumps combined with the passing of the heated gaseous drying medium across the coal lumps serving to dry the coal lumps and to cause coal dust to emit from the coal lumps thereby causing the gaseous drying medium to become coal dust-laden, removing the coal dust-laden gaseous drying medium from the container, separating at least some of the coal dust from the drying medium, storing at least a portion of the coal dust thus separated, feeding in a regulated manner at least some of the stored coal dust to the combustion process, burning the dust as a fuel in the combustion process, and removing dried coal from the container as an end product, said dried coal lumps being uncrushed and of sufficiently large sizes, relative to their sizes prior to the drying operation, that the said dried coal lumps are suitable for shipment from the mine as lump coal.

8. A method according to claim 7, wherein some of the coal dust which is not needed for combustion is discharged from the system between the separation and storage steps.

9. A method according to claim 7, wherein said regulated feeding includes sensing the temperature of the system between the commencement of the combustion stage and the termination of the separating stage and controlling the feeding in accordance with said temperature in order to maintain the temperature of the drying medium Within predetermined limits.

10. A method according to claim 7 wherein temporary excess coal dust is delivered to the storage station and wherein said excess coal dust is removed from the storage station and returned to a point in the system remote from the storage station in order to prevent the development of explosive conditions at the storage station.

References Cited in the file of this patent UNITED STATES PATENTS 1,173,510 Hermansen Feb. 29, 1916 1,910,735 Zikesch May 23, 1933 1,943,949 Coghlan et a1. Jan. 16, 1934 2,259,967 Vogel-Jorgensen Oct. 21, 1941 2,728,311 Campbell Dec. 27, 1955 2,877,562 Krantz Mar. 17, 1959 

